Many searches for extraterrestrial communication signals focus on a region of the electromagnetic spectrum in radio wavelengths between 18 cm and 21 cm , a region where our Galaxy's various components collectively emit the most weakly. Let's explore why even this small region of the spectrum is hard to explore. Radio emission has low energy and is not typically very bright. Suppose it takes 48 minutes to get a suitable measurement of a given channel. How long would it take one radio telescope to search every channel of just one star? Express your answer in years